U.S. patent application number 17/055428 was filed with the patent office on 2021-06-24 for torque transmission device with reduced friction.
This patent application is currently assigned to SAFRAN AIRCRAFT ENGINES. The applicant listed for this patent is SAFRAN AIRCRAFT ENGINES. Invention is credited to Stephane Pierre Guillaume BLANCHARD, Helene Myriam CONDAT, Laurent Paul Francois PERROT, Nicolas Xavier TRAPPIER.
Application Number | 20210189972 17/055428 |
Document ID | / |
Family ID | 1000005496196 |
Filed Date | 2021-06-24 |
United States Patent
Application |
20210189972 |
Kind Code |
A1 |
BLANCHARD; Stephane Pierre
Guillaume ; et al. |
June 24, 2021 |
TORQUE TRANSMISSION DEVICE WITH REDUCED FRICTION
Abstract
The invention relates to a turbomachine comprising a
low-pressure shaft (27) configured to drive a fan shaft (32) in
rotation by means of a coupling assembly comprising a first shaft
(1) on which are formed a plurality of first axial grooves (7), a
second shaft (2) on which are formed a plurality of second axial
grooves (12), and a coupling device (4) including a plurality of
rolling elements (13) and an annular cage (14) positioned between
the first shaft (1) and the second shaft (2), the rolling elements
(13) being positioned between one of the first axial grooves (7)
and one of the second axial grooves (12) to couple in rotation the
first and the second shaft (1, 2), each first and second groove (7,
12) having a first (16) and a second (17) substantially planar
surface inclined with respect to one another and extending along
the axis.
Inventors: |
BLANCHARD; Stephane Pierre
Guillaume; (MOISSY-CRAMAYEL, FR) ; CONDAT; Helene
Myriam; (MOISSY-CRAMAYEL, FR) ; TRAPPIER; Nicolas
Xavier; (MOISSY-CRAMAYEL, FR) ; PERROT; Laurent Paul
Francois; (MOISSY-CRAMAYEL, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAFRAN AIRCRAFT ENGINES |
Paris |
|
FR |
|
|
Assignee: |
SAFRAN AIRCRAFT ENGINES
Paris
FR
|
Family ID: |
1000005496196 |
Appl. No.: |
17/055428 |
Filed: |
May 15, 2019 |
PCT Filed: |
May 15, 2019 |
PCT NO: |
PCT/FR2019/051098 |
371 Date: |
November 13, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F05D 2250/294 20130101;
F05D 2240/60 20130101; F16D 2001/103 20130101; F02C 7/36 20130101;
F16D 3/065 20130101 |
International
Class: |
F02C 7/36 20060101
F02C007/36; F16D 3/06 20060101 F16D003/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2018 |
FR |
1854044 |
Claims
1.-11. (canceled)
12. A turbomachine including a casing (35), a low-pressure shaft
(27) mounted in rotation in the casing (35), a fan shaft (32)
mounted in rotation relative to the casing (35) and a coupling
assembly, the low-pressure shaft (27) being configured to drive the
fan shaft (32) in rotation by means of the coupling assembly, the
coupling assembly including: a first shaft (1) which extends along
an axis (X) and [is] integral with one among the low-pressure shaft
(27) and the fan shaft (32), the first shaft (1) comprising at
least a first portion (5) having an outer face (6) in which are
formed a plurality of first axial grooves (7), a second shaft (2)
coaxial with the first shaft (1) and integral with one among the
low-pressure shaft (27) and the fan shaft (32), the second shaft
(2) comprising at least one second portion (8) which surrounds the
first portion (5) and has an inner face (11) in which are formed a
plurality of second axial grooves (12), a coupling device (4)
including a plurality of rolling elements (13) and an annular cage
(14), said cage (14) being positioned between the first shaft (1)
and the second shaft (2), a plurality of recesses (15) being formed
in the cage (14), each of the rolling elements (13) begin
positioned on the one hand in a respective recess (15) and on the
other hand between one of the first axial grooves (7) and one of
the second axial grooves (12) so as to couple in rotation the first
and the second shaft (1, 2), the dimensions of one of the rolling
elements (13) and the positioning of one of the second grooves (12)
relative to one of the first grooves (7) being configured to supply
a radial and tangential clearance to one of the rolling elements
(13), and in which each first and second groove (7, 12) has a first
(16) and a second (17) substantially planar surface extending along
the axis, the first (16) and the second (17) surfaces being
inclined relative to one another.
13. The turbomachine according to claim 12, wherein each rolling
element (13) is mounted free in its respective recess (15).
14. The turbomachine according to claim 12, wherein the recesses
(15) of the cage (14) are axially aligned so as to form a series of
axial rows, the axial rows being distributed angularly in regular
fashion around the axis (X) so that each row extends along a first
axial groove (7) and a second axial groove (12).
15. The turbomachine according to claim 12, wherein the rolling
elements (13) comprise balls.
16. The turbomachine according to claim 12, wherein the coupling
device (4) is movable in translation along the axis (X).
17. The turbomachine according to claim 12, wherein the coupling
assembly further comprises a first return element (19) extending
between the cage (14) and one among the first shaft (1) and the
second shaft (2), the first return element (19) being configured to
define the axial position of the cage (14) relative to one among
the first portion (5) and the second portion (8).
18. The turbomachine according to claim 17, wherein one among the
first portion (5) and the second portion (8) has a first axial
abutment (20), the cage (14) having a second axial abutment (22),
the first return element (19) being supported on each of these
axial abutments (20, 22).
19. The turbomachine according to claim 12, comprising a second
return element (19') extending between the cage (14) and the
portion among the first portion (5) and the second portion (8)
which has the first abutment (20), the second return element (19')
being configured to define the axial position of the cage (14)
relative to said portion among the first portion (5) and the second
portion (8) which has the first abutment (20).
20. The turbomachine according to claim 19, wherein the portion
among the first portion (5) and the second portion (8) which has
the first abutment (20) also has a third abutment (21), and the
cage (14) also has a fourth abutment (23), the second return
element (19') being supported on the third abutment (21) and the
fourth abutment (23).
21. The turbomachine according to claim 17, further comprising a
second return element (19') extending between the cage (14) and the
portion among the first portion (5) and the second portion (8)
which has the first abutment (20), the second return element (19')
being configured to define the axial position of the cage (14)
relative to said portion among the first portion (5) and the second
portion (8) which has the first abutment (20), wherein the first
return element (19) and the second return element (19') extend on
either side of the cage (14).
22. The turbomachine according to claim 12, wherein the
low-pressure shaft (27) includes a turbine portion (34) attached to
the low-pressure turbine (26) and a rear abutment portion (35)
attached axially to the casing (36) of the turbomachine and guided
in rotation relative to the casing (36), the turbine portion (34)
and the rear abutment portion (35) being coupled by means of a
splined coupling.
Description
GENERAL TECHNICAL FIELD AND PRIOR ART
[0001] The invention belongs to the technical field of power
transmission elements, and more particularly to the transmission of
torque and of a rotating movement between two shafts, particularly
in a turbomachine.
[0002] In mechanical systems like those shown schematically in FIG.
1, comprising two or more shafts driven in rotation along a
longitudinal axis X, it is sometimes necessary, for reasons of
mechanical strength of the system, that a degree of freedom in
longitudinal translation exist between an engine shaft, here a
first shaft 1 mounted in rotation on a chassis 3, and a driven
shaft, here a second shaft 2 mounted in rotation and in translation
relative to the chassis 3, and mounted in translation relative to
the first shaft 1.
[0003] Conventional solutions, such as splined couplings, allow the
transmission of large torques between a first shaft 1 and a second
shaft 2 while allowing relative axial translation of the
shafts.
[0004] Solutions of this type have, however, the disadvantage of
including large surface areas in contact, generating non-negligible
friction during axial movement of a shaft relative to the other
when the transmitted torque is high.
[0005] Besides the energy loss that this friction causes, causing
local heating of the parts and a decrease in efficiency of power
transmission from one shaft to the other, until it prevents the
relative movement of the first shaft 1 and of the second shaft
2.
[0006] This damping can have a detrimental effect on the vibration
behavior of the system.
[0007] In fact, this phenomenon of variable resisting force on a
supposed degree of freedom of the system modifies the stiffness of
the system, and thus shifts the natural modes of vibration of the
system relative to the natural modes of a model in which the energy
is transmitted without losses.
[0008] The shifting of the natural modes can cause the frequency of
these natural modes to approach the frequencies of the harmonics of
the vibrations generated by the system in operation.
[0009] The dissipation of energy by the system can be altered by
it, and thus cause the system to vibrate significantly, leading to
a degradation of the system and possibly causing the destruction by
fatigue of an element of the system.
[0010] These problems are particularly critical in a turbomachine,
particularly as regards the coupling of the different portions of a
shaft allow transmission of power between different elements. In
fact, in the case in which the shaft is divided into different
portions, it is necessary to achieve coupling to transmit movement
between the different parts of the shaft.
[0011] Therefore, there exists a need to limit the potential energy
losses of a mechanical connection transmitting rotary power from
one shaft to another, particularly when the power levels present
involve large torques.
GENERAL PRESENTATION OF THE INVENTION
[0012] The invention has as its object to limit the energy losses
of a mechanical connection transmitting rotary power, particularly
between a low-pressure shaft of a turbomachine and a fan shaft of a
turbomachine.
[0013] Another object of the invention is to allow the transmission
of large torques while ensuring relative translation movement
between two elements.
[0014] Another object of the invention is to limit the impact of
the transmission on the vibration behavior of the system,
particularly when it is subjected to large vibration loads. [0015]
To this end, the invention proposes a turbomachine including a
casing, a low-pressure shaft mounted in rotation in the casing, a
fan shaft mounted in rotation relative to the casing and a coupling
assembly, the low-pressure shaft being configured to drive the fan
shaft in rotation by means of the coupling assembly, the coupling
assembly including: [0016] a first shaft which extends along an
axis integral with one among the low-pressure shaft and the fan
shaft, the first shaft comprising at least one first portion having
an outer face in which are formed a plurality of first axial
grooves, [0017] a second shaft coaxial with the first shaft and
integral with one among the low-pressure shaft and the fan shaft,
the second shaft comprising at least one second portion with
surrounds the first portion and has an inner face in which are
formed a plurality of second axial grooves, [0018] a coupling
device including a plurality of rolling elements and an annular
cage, said cage being positioned between the first shaft and the
second shaft, a plurality of recesses being formed in the cage,
each of the rolling elements being positioned on the one hand in a
respective recess and on the other hand between one of the first
axial grooves and one of the second axial grooves so as to couple
in rotation the first and the second shaft, and in which each first
and second groove has a first and a second substantially planar
surface extending along the axis, the first and the second surfaces
being inclined relative to one another.
[0019] In this manner, the rolling elements allow forming obstacles
by cooperating with the grooves so as to transmit the torque from
one shaft to the other, while still allowing rolling in the grooves
and thus ensuring a translation movement between the shafts during
which friction is strongly limited.
[0020] The energy losses of the mechanical connection thus formed
are therefore strongly limited.
[0021] The vibration behavior of the system is preserved.
[0022] Optionally but advantageously, the invention can be
completed by the following characteristics, taken alone or in
combination: [0023] each rolling element is mounted free in
rotation in its respective recess; [0024] the recesses of the cage
are axially aligned so as to form a series of axial rows, the axial
rows being distributed angularly in regular fashion around the axis
so that each row extends along a first axial groove and a second
axial groove; [0025] the rolling elements comprise balls; [0026]
the coupling device is movable in translation along the axis;
[0027] the assembly also comprises a first return element extending
between the cage and one among the first shaft and the second
shaft, the first return element being configured to define the
axial position of the cage relative to one among the first portion
and the second portion; [0028] said one among the first portion and
the second portion has a first axial abutment, the cage having a
second axial abutment, the first return element being supported on
each of these axial abutments; [0029] the assembly also comprise a
second return element extending between the cage and the portion
among the first portion and the second portion which has the first
abutment, the second return element being configured to define the
axial position of the cage relative to said portion among the first
portion and the second portion which has the first abutment; [0030]
the portion among the first portion and the second portion which
has the first abutment also has a third abutment, and the cage also
has a fourth abutment, the second return element being supported on
the third abutment and the fourth abutment; [0031] the first return
element and the second return element extend on either side of the
cage; [0032] the low-pressure shaft includes a turbine portion
attached to the low-pressure turbine and a rear abutment portion
attached axially to the casing of the turbomachine and guided in
rotation relative to the casing, the turbine portion and the rear
abutment portion being coupled by means of a splined coupling.
PRESENTATION OF THE FIGURES
[0033] Other features and advantages of the invention will still be
revealed by the description that follows, which is purely
illustrative and not limiting, and must be read with reference to
the appended figures in which:
[0034] FIG. 1 is a kinematic schematic of a system conforming to
the prior art;
[0035] FIG. 2 is a partial section view in perspective of a
mechanical assembly conforming to the invention;
[0036] FIG. 3 is a section profile view of an assembly conforming
to the invention;
[0037] FIG. 4 is a section front view of an assembly conforming to
the invention;
[0038] FIG. 5 is a detail view of the assembly of an obstacle
element in an embodiment of an assembly conforming to the
invention;
[0039] FIG. 6 is a developed view of a frontal section of an
assembly conforming to the invention, highlighting the relative
position of a first groove, a second groove and an obstacle element
during the driving of one shaft by the other; more particularly
FIG. 6a shows a plurality of obstacle elements comprised between a
developed internal portion and a developed external portion; FIG.
6b shows in detail the placement of an obstacle element relative to
a first groove and a second groove during driving;
[0040] FIG. 7 is a schematic profile view showing an embodiment of
an assembly conforming to the invention;
[0041] FIG. 8 is an assembly figure of a turbomachine according to
the invention;
[0042] FIG. 9 is a detail view of the coupling between the
low-pressure shaft and the fan shaft of a turbomachine according to
the invention;
[0043] FIG. 10 is a detail view of the coupling between the turbine
portion and the rear abutment portion of the low-pressure shaft of
a turbomachine according to the invention.
DESCRIPTION OF ONE OR MORE IMPLEMENTATION MODALITIES AND
EMBODIMENTS
[0044] The invention can apply to any mechanical system including a
first rotating shaft and a second rotating shaft, for example in a
turbomachine in which a transmission shaft is divided into several
portions coupled to one another by means of a coupling
assembly.
[0045] A coupling assembly is shown schematically in FIG. 1 and
comprises: [0046] a first rotating shaft 1 comprising at least one
first portion 5 having an axis of revolution X, said first portion
5 having an outer face 6 in which are formed a plurality of first
axial grooves 7, [0047] a second shaft 2 comprising at least a
second portion 8 having an inner face 11 in which are formed a
plurality of second grooves 12, said second shaft 2 being coaxial
with the first shaft 1 and [0048] a coupling device 4 configured to
allow power transmission between the first shaft 1 and the second
shaft 2.
[0049] In the present application, the axis of revolution of the
first shaft 1 is called the axis X of rotation of the first
rotating shaft 1. The axial direction corresponds to the direction
of the axis X of the first shaft 1, and a radial direction is a
direction perpendicular to this axis and passing through it.
Likewise, an axial plane is a plane containing the axis X and a
radial plane is a plane perpendicular to this axis X and passing
through it. The tangential direction is a direction perpendicular
to the axis X and not passing through it. The circumferential
direction is a direction which extends around the axis X. Unless
otherwise stated, inner and outer, respectively, will be used with
reference to a radial direction so that the inner (i.e. radially
inner) portion or face of an element is closer to the axis X than
the outer (i.e. radially outer) portion or face of the same
element.
[0050] FIG. 2 illustrates an embodiment in which the first shaft 1
is coaxial with the axis of revolution X of the first portion
5.
[0051] The second shaft 2 comprises a second portion 8 extending
along the axis of the first portion 5 and having a substantially
cylindrical cavity 9 configured to receive the first portion 5 of
the first shaft 1.
[0052] In the embodiment illustrated, the second shaft 2 and the
second portion 8 extend along the axis X. However, as a variant,
the second portion 8 can extend along an axis parallel to the axis
of the second shaft 2.
[0053] The coupling device 4 includes a plurality of rolling
elements 13 and a substantially cylindrical cage 14.
[0054] The cage 14 extends between the first portion 5 of the first
shaft 1 and the second portion 8 of the second shaft 2 so that it
is comprised radially between the outer face 6 and the inner face
11.
[0055] Moreover, a plurality of recesses 15 is formed in the cage
14. The rolling elements 13 are each positioned, on the one hand,
in a respective recess 15 and on the other hand between one of the
first axial grooves 7 and one of the second axial grooves 12 so as
to transmit a tangential force from one among said first groove 7
and said second groove 12 to the other among said first groove 7
and said second groove 12.
[0056] The rolling elements 13 can comprise rollers and/or balls.
They ensure the transmission of the torque by obstacle between the
first shaft 1 and the second shaft 2 and allow eliminating direct
contact between the first shaft 1 and the second shaft 2.
[0057] In this manner, friction is strongly reduced during relative
axial movement of the first shaft 1 and the second shaft 2, which
allows relative axial movement of the first shaft 1 and of the
second shaft 2 even when large torques are transmitted from one
shaft to another.
[0058] This also allows reducing the dissipation of energy by
friction, and therefore improving the efficiency of power
transmission, and limiting the variations of stiffness of the
mechanical connection and therefore of the assembly.
[0059] This therefore allow limiting the shifting of the natural
modes of the assembly and limits the risk of appearance of resonant
phenomena. The lifetime and the reliability of the assembly are
consequently considerably increased.
[0060] In one embodiment, each rolling element 13 is free in its
respective recess 15 of the cage 14 so as to be able to freely move
in translation in the first axial groove 7 and in the corresponding
second axial groove 12. This embodiment allows further reduction of
friction in the case of axial movement, and therefore further
increases the lifetime and the reliability of the assembly.
[0061] The recesses 15 are configured to position the rolling
elements 13 relative to one another, which allows in particular
avoiding the rolling elements 13 being in contact with one
another.
[0062] The recesses 15 of the cage 14 thus allow avoiding friction
between the rolling elements 13, causing energy losses, and which
could lead to the blocking of certain rolling elements 13 leading
to a degradation of the coupling assembly.
[0063] In the embodiment illustrated in FIG. 3, the rolling
elements 13 are distributed axially in a regular spacing.
[0064] This therefor allows axial distribution of the rolling
elements 13 along the first 7 and second 12 grooves, so as to
distribute the points of contact on a wider area and to limit the
level of local loads in the first portion 5 and the second portion
8.
[0065] In particular, this allows minimizing the fatigue of the
rolling elements 13, of the first 7 and second 12 grooves and thus
increasing the lifetime of the coupling assembly.
[0066] FIG. 4 illustrates the angular distribution, around the axis
X, of the first 7 and second 12 grooves, of the rolling elements 13
and consequently of the recesses 15.
[0067] The angular pitch p between two adjacent second grooves 12
is constant, and identical to the angular pitch between two
adjacent first grooves 7, likewise for two adjacent rolling
elements 13 and two adjacent rows of recesses 15.
[0068] In this manner, the distribution of loads in the first
portion 5 and the second portion 8 is optimized and allows limiting
the peaks of the loads.
[0069] In the detail view illustrated in FIG. 5, a ball is set in
position by a recess 15 of the cage 14, the cage 14 being
configured to retain the rolling elements 13 in position relative
to one another, as well as to retain them in position against the
first portion 5, inside the cage 14.
[0070] In a variant that is not shown, the cage 14 is configured to
retain the rolling elements 13 in position against the second
portion 8 outside the cage 14.
[0071] The cage 14 therefore allows in particular facilitating the
assembly of the rolling elements 13 on one of the shafts before
bringing the first shaft 1 and the second shaft 2 into their
relative positions.
[0072] FIG. 6a illustrates the relative tangential position of the
rolling elements 13, of the first grooves 7 and of the second
grooves 12 when torque is transmitted by the first shaft 1 to the
second shaft 2. In FIG. 6a, an angular portion of a straight
section of the assembly is shown as developed along a straight
line.
[0073] A detail of a configuration of this type is illustrated in
FIG. 6b. A first groove 7, in the same manner as a second groove
12, includes a first 16 and a second 17 planar surface extending
longitudinally.
[0074] The first surface 16 and the second surface 17 are inclined
relative to one another and join together while forming a groove
bottom 18. A groove 7, 12 thus forms, in this preferred embodiment,
a dihedral of which the apex angle allows transmitting tangential
forces to the corresponding rolling element 13 regardless of the
direction of rotation of the first shaft 1 or of the second shaft
2.
[0075] In other embodiments, not shown, the number of surfaces
forming a groove 7, 12 can be greater, for example 3 or 4, so as to
form a trough housing the rolling elements 13.
[0076] Thanks to the first and second surfaces 16, 17 inclined
relative to one another, a tangential force can be transmitted
between the first 1 and the second 2 shaft in both directions,
allowing transmission of torque (or power) regardless of the
direction of rotation of the shafts.
[0077] The dimensions of a rolling element 13 and the positioning
of a second groove 12 relative to a first groove 7 are configured
to provide radial and tangential clearance to the rolling element
13. In this manner, the blocking of a rolling element between a
second groove 12 and a first groove 7 is avoided, particularly
during the relative axial movement of the first shaft 1 and of the
second shaft 2.
[0078] In addition, this allows reducing the number of points of
contact between the rolling element 13 and the grooves when torque
is transmitted, and thus reducing friction between the rolling
element 13 and the grooves 7, 12. In fact, a rolling element 13
being positioned between two grooves 7, 12, an absence of radial
and tangential clearance of the rolling element 13 would imply that
it had two points of contact with a first groove 7, and two points
of contact with a second groove 12.
[0079] In the case shown, the rolling element 13 has only one point
of contact with the first groove 7 and has two points of contact
with the second groove 12. In fact, during operation, the
centrifugal force applied to the rolling elements 13 pushes them
into contact with the radially outer groove, here the second groove
12. The three contact points thus prevent any relative movement in
the tangential direction between the rolling element 13 and the
grooves 7, 12.
[0080] Thus, force is transmitted from one surface of a first
groove 7 to a surface of a second groove 12, thus accomplishing the
transmission of torque from one shaft to the other.
[0081] In a variant, not shown, a rolling element 13 has only a
single point of contact with a first groove 7 and one point of
contact with a second groove 12, particularly when the torque
transmitted is sufficiently large, despite the centrifugal force
applied to the rolling element 13, to move the rolling element 13
tangentially in an over-center position in a tangential direction
between a first surface 16 of one among a first groove 7 and a
second groove 12 and a second surface 17 of the other among the
first groove 7 and the second groove 12.
[0082] In this manner, friction is further reduced, and this also
allows facilitating the relative movement of the first shaft 1 and
of the second shaft 2 when a large torque is transmitted.
[0083] In one variant, not shown, the diameter of the outer face 6
of the first portion 5 and the diameter of the inner face 11 of the
second portion 8 are configured so as to cooperate with the
smallest positive clearance, allowing centering between the two
shafts.
[0084] The grooves of the rolling element 13 are also configured so
as to prevent the rolling element 13 from leaving the first groove
7 or the second groove 12. To this end, the distance in a radial
direction between the inner face 11 and the outer face 6 is less
than the diameter of a rolling element 13.
[0085] Depending on the torque to be transmitted by the coupling
device 4, the number and the characteristics of the rolling
elements 13 can vary, particularly in order to limit the Hertz
pressures and avoid plastic deformation of the rolling elements
13.
[0086] During the driving of one shaft by the other, the
translation movements of the shafts can cause successive
translations of the cage 14.
[0087] When these successive translations bring the cage 14 to one
of the ends of the grooves 7, 12, rolling elements 13 can become
blocked between the first shaft 1 and the second shaft 2, or leave
their respective recesses 15 and grooves 7, 12, which can cause
degradation of the coupling device 4.
[0088] In one embodiment, a first return element 19 extends between
the cage 14 and one among the first portion 5 and the second
portion 8, said first return element 19 being configured to move
the cage 14 axially relative to the portion on which the return
element is supported.
[0089] To this end, the portion among the first portion 5 and the
second portion 8 has a first axial abutment 20, the cage 14 having
a second axial abutment 22, and the first return element 19 is
supported on the first abutment 20 and the second abutment 22.
[0090] When the return element 19 is compressed, it can therefore
develop a thrust force on the cage 14 and move said cage 14.
[0091] This allows avoiding the rolling elements 13 moving axially
until one of the ends of the grooves 7, 12 and causing the
degradation of the coupling device 4.
[0092] In one variant, the return element 19 is attached to the
first abutment 20 and the second abutment 21. In this manner, the
return element 19 can operate in compression and in tension and
cause movement of the cage 14 in two opposite directions. This
allow returning the cage 14 regularly to a predefined axial
position which allows optimal operation of the coupling device
4.
[0093] During driving, the torque transmitted generates a large
clamping force from the first portion 5 and from the second portion
8 on the rolling elements 13. During clamping of the rolling
elements 13 by the first 5 and second 8 portion, said rolling
elements 13, and therefore incidentally the cage 14, can only move
relative to the portions 5, 8 if said portions 5, 8 are moving
relative to one another.
[0094] When the transmitted torque is reduced, and incidentally the
clamping force applied to the rolling elements 13 is reduced, for
example during a transition in the torque or a deceleration,
tangential clearance appears between the rolling elements 13 and
the grooves 7, 12 and allows the return element 19 to replace the
cage 14 in the predetermined position relative to the portion among
the first portion 5 and the second portion 8 which has the first
abutment 20.
[0095] In an embodiment shown in FIG. 7, the coupling device 4 also
includes a second return element 19'.
[0096] The portion among the first portion 5 and the second portion
8 which has the first abutment 20 also has a second abutment
21.
[0097] The cage also has a fourth abutment 23.
[0098] The first return element 19 is supported, on the one hand,
on the first abutment 20 and on the other hand on the second
abutment 22, the second return element 19' being supported on the
one hand on the third abutment 21 and on the other on the fourth
abutment 23.
[0099] In this manner, the axial position of the cage 14 relative
to the first shaft 1 is constrained to an optimal position. It is
not necessary to attach the return element to abutments, each
return element 19, 19' being able to work in compression, which
facilitates assembly and manufacture.
[0100] The force developed by the two return elements 19, 19' is
also greater than the force developed by a single return element
and allows returning the cage 14 into position more rapidly and
accurately.
[0101] A turbomachine 24 illustrated in FIG. 8 includes a
low-pressure body and a high-pressure body.
[0102] The low-pressure body includes a low-pressure compressor 25,
a low-pressure turbine 26 and a low-pressure shaft 27 configured to
transmit power from the low-pressure turbine 26 to the low-pressure
compressor 25, the high-pressure body including a high-pressure
compressor 28, a high-pressure turbine 29 and a high-pressure shaft
30 configured to transmit power from the high-pressure turbine 29
and the high-pressure compressor 28.
[0103] In the embodiment shown, the low-pressure body drives in
rotation a fan body including a fan 31 mounted fixed on a fan shaft
32.
[0104] A flow of air circulates in the turbomachine and passes,
from upstream to downstream, the fan 31, the low-pressure
compressor 25, the high-pressure compressor 28, a combustion
chamber 33, the high-pressure turbine 29 then the low-pressure
turbine 26.
[0105] The low-pressure shaft 27 drives in rotation the fan shaft
32 by means of a coupling assembly as previously described. The
coupling device 4 is thus disposed between the low-pressure shaft
27 and the fan shaft 32.
[0106] In the embodiment shown in FIG. 9, the fan shaft 32 can be
likened to the second shaft 2 and has a plurality of second grooves
12 formed on its inner face 11, the fan shaft 27 being likened to
the first shaft 1 and having a plurality of first grooves 7 formed
on its outer face 6.
[0107] In one variant, the fan shaft 32 can be likened to the first
shaft 1 and the low-pressure shaft 27 can be likened to the second
shaft 2.
[0108] In the embodiment shown in FIG. 10, the low-pressure shaft
27 is segmented into several portions, and comprises in particular
a turbine portion 34 attached to the low-pressure turbine 26 and a
rear abutment portion 35 attached axially to the casing 36 of the
turbomachine and guided in rotation relative to the casing 36 of
the turbomachine.
[0109] A splined coupling 37 is accomplished between the turbine
portion 34 and the rear abutment portion 35. A coupling of this
type has a high temperature tolerance, which allows this coupling
to retain its mechanical characteristics and its reliability even
if it rises in temperature.
[0110] The use of a splined coupling between the turbine portion 34
and the rear abutment portion 35 therefore allows retaining the
mechanical characteristics of the coupling despite its positioning
in proximity to and in contact with hot parts, particularly the
low-pressure turbine 26 through which hot gases at high temperature
transit.
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